Learning objectives
1. Nature of viruses, host range, size, structure & life cycle
2. How Viruses are classified & named
3. DNA & RNA viruses
4. Reproductive strategies of animal viruses
5. Viral diseases
- HIV, Influenza, viral tumors
Viruses
- Complexes of molecules that are capable of infecting cells Own target cells (specific cells)
- Viruses contain either DNA or RNA enclosed in a protein coat (capsid) naked virus
Double or single stranded nucleic acid
Some contain additional lipoprotein envelope
- Viruses must make use of the hosts cellular machinery to reproduce and survive (i.e. obligate intracellular parasites) must go inside cell to reproduce
So are viruses alive?
Are viruses alive?
- Possess genes, replicate, evolve & are adapted to particular hosts & habitats
however, viruses cannot capture & store free energy
They are not functionally active outside their host cells
- A virus becomes part of a living system only after it has infected a host cell & its genome becomes integrated with that of the cell
- Replicate only through the metabolic activities of infected cells
Therefore viruses are classified as non-living infectious entities
Can’t capture & store free energy. Viruses need hosts to reproduce
Viruses
- can infect Prokaryotes & Eukaryotes
(Prokaryote virus = bacteriophage)
- most viruses infect only specific types of cells in one host (called specific viruses); if not specific, called generalistic viruses.
- Host range os determined by specific host attachment sites & cellular factors
- recognize cell membrane proteins (receptors), which have an alternate function in “normal” cell physiology
Viral Structures
SPIKES: attachment to host cell
Capsid will wrap up genome
Pins will anchor itself onto cell wall
Enveloped virus pseudumembrane wraps up DNA?
Bilayer membranes can regulate.
Spikes important to attachement
Helical Viruses
Nucleic acid
Ebola virus is extremely dangerous. Very easy...